[CraigS]

Scientists discover quantum fingerprints of chaos

Chaotic behavior is the rule, not the exception, in the world we experience through our senses, the world governed by the laws of classical physics.
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Even tiny, easily overlooked events can completely change the behavior of a complex system, to the point where there is no apparent order to most natural systems we deal with in everyday life.
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Scientists who study "chaos" - which they define as extreme sensitivity to infinitesimally small tweaks in the initial conditions - have observed this kind of behavior only in the deterministic world described by classical physics.

Note: Chaotic behaviours are displayed in classical deterministic systems now they're chasing evidence of chaos in quantum systems …

If the starting point for a quantum particle cannot be precisely known, then there is no way to construct a theory that is sensitive to initial conditions in the way of classical chaos.
Yet quantum mechanics is the most complete theory of the physical world, and therefore should be able to account for all naturally occurring phenomena.
"The problem is that people don't see [classical] chaos in quantum systems," said Professor Poul Jessen of the University of Arizona. "And we believe quantum mechanics is the fundamental theory, the theory that describes everything, and that we should be able to understand how classical physics follows as a limiting case of quantum physics."

EXPERIMENTS REVEAL CLASSICAL CHAOS IN QUANTUM WORLD
Now, however, Jessen and his group in UA's College of Optical Sciences have performed a series of experiments that show just how classical chaos spills over into the quantum world.
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The scientists report their research in the Oct. 8 issue of the journal Nature in an article titled, "Quantum signatures of chaos in a kicked top."
Their experiments show clear fingerprints of classical-world chaos in a quantum system designed to mimic a textbook example of chaos known as the "kicked top."
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One of the most dramatic quantum signatures the team saw in their experiments was directly visible in their images: They saw that the quantum spinning top observes the same boundaries between stability and chaos that characterize the motion of the classical spinning top. That is, both quantum and classical systems were dynamically stable in the same areas, and dynamically erratic outside those areas.

They go on to say they've revealed the signature of chaos which is related to entanglement …

A NEW SIGNATURE OF CHAOS CALLED 'ENTANGLEMENT'
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In Jessen's experiment, the electron and nuclear spins remained unentangled as a result of stable quantum dynamics, but rapidly became entangled if the dynamics were chaotic.

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